The inflammatory response induced by rhinovirus is characterized by the predominance of airway[unreadable] neutrophils that correlates with the severity of asthma exacerbation. Despite considerable recent evidence[unreadable] that supports the importance of neutrophils in the pathogenesis of asthma, there is limited understanding of[unreadable] how rhinovirus modulates neutrophil function. The long-term goal of this proposal is to characterize the[unreadable] signaling mechanisms by which respiratory viral infections induce neutrophil motility and[unreadable] recruitment to the airway, and to identify novel therapeutic targets that limit viral-induced[unreadable] inflammatory responses. Substantial evidence suggests that rhinovirus infections induce neutrophilic[unreadable] inflammation indirectly by promoting the release of inflammatory mediators from airway epithelial cells. We[unreadable] now have exciting new data that indicate that rhinovirus 16 also has direct effects on neutrophil signaling and[unreadable] motility. With our established expertise in live fluorescent imaging and recently developed novel technology[unreadable] to analyze chemotaxis using microfluidics, we are uniquely positioned to test the following hypothesis. We[unreadable] propose that rhinovirus, by both indirect and direct interactions with neutrophils, modulates[unreadable] signaling pathways critical for neutrophil migration and chemotaxis, and thereby affects the[unreadable] recruitment and retention of neutrophils in the airway. We propose the following Specific Aims: I.[unreadable] Elucidate the mechanisms of neutrophil chemotaxis and recruitment to the airway in response to[unreadable] respiratory viral infection. Calpain inhibition blocks neutrophil chemotaxis to IL-8 in vitro. Using both in[unreadable] vitro and in vivo approaches with transgenic mouse models in collaboration with Project IV, we propose to[unreadable] characterize how calpains regulate neutrophil chemotaxis and inflammatory recruitment in response to[unreadable] respiratory viral infection in vivo. II. Dissect the molecular mechanisms by which rhinovirus modulates[unreadable] TNFalpha-mediated neutrophil function. TNFalpha promotes a stop signal that triggers neutrophil adhesion and[unreadable] inhibits cell migration. Our recent studies indicate that rhinovirus perturbs TNFalpha-mediated effects. In[unreadable] addition, preliminary data indicate that rhinovirus may affect neutrophil function directly via activation of ERK[unreadable] and p38 MARK pathways. In collaboration with Project II and V, we now propose to dissect the molecular[unreadable] mechanisms by which rhinovirus modulates TNFalpha-mediated neutrophil adhesion and signaling. III. Examine[unreadable] the effect of rhinovirus on neutrophil motility and chemotaxis. Preliminary findings indicate that[unreadable] rhinovirus directly induces neutrophil random motility and reduces chemotactic migration through an ICAM-1-[unreadable] dependent pathway.. Using time lapse microscopy, we now propose to dissect the mechanisms by which[unreadable] rhinovirus modulates neutrophil migration and chemotaxis, and in collaboration with Project I determine if[unreadable] these mechanisms are different in patients susceptible to rhinovirus-induced asthma exacerbation.